1. Field of the Invention
This invention relates to apparatus for holding guide vanes such as air flow turning vanes in a duct.
2. Description of the Prior Art
Turning vanes are used to direct moving gases around duct corners where the ends of two ducts positioned at right angles intersect, such as heating or ventilation air ducts. If vanes are not used, air strikes the wall of the intersecting duct. This can cause turbulence or backflow in the duct. The vanes are positioned diagonally across the duct corner region to guide the air flow smoothly around the corner.
A commonly used turning vane is constructed by joining two pieces of curved sheet metal, having different radii of curvature, at their edges. This results in a hollow vane with a crescent-shaped cross section. The vane can be cut to whatever length is needed in a duct.
Although the vanes are easily constructed, the positioning and fastening of the vanes in an assembly which permits proper positioning in a duct is an expensive and labor-intensive process. Many techniques for fastening these vanes to a pair of sheet metal rails or to the ducts themselves have been tried. These techniques are not satisfactory because they involve using special fasteners or expensive tooling on the sheet metal.
A search of fasteners used in sheet metal attachment uncovered the following U.S. patents:
______________________________________ Inventor U.S. Pat. No. Date of Issue ______________________________________ Husted 3,350,124 10/31/67 Friedling et al 3,511,525 05/12/70 Friedling et al 3,606,415 09/20/71 Hallock, Jr. 3,812,817 05/28/74 Graham et al 3,837,136 09/24/74 Mez 3,919,826 11/18/75 Mez 4,154,547 05/15/79 Smitka 4,297,049 10/27/81 ______________________________________
U.S. Pat. No. 3,350,124 to Husted discloses a method of curling an edge of a sheet into a closed loop and interlocking the loop with grooved parts.
U.S. Pat. No. 3,812,817 to Hallock, Jr. shows a hollow sheet metal nail designed for attachment in lightweight cement-based building materials. This fastener is not used to attach pieces of sheet metal.
U.S. Pat. No. 3,606,415 to Friedling et al discloses a connecting device for attaching two sheet metal plates at an angle. U.S. Pat. No. 3,511,525, also to Friedling et al, shows another connecting device for fastening sheet metal in perpendicular positions.
Two U.S. patents to Mez, U.S. Pat. No. 3,919,826, and U.S. Pat. No. 4,154,547, show connectors for joining two sheets of sheet metal in perpendicular fashion.
U.S. Pat. No. 4,297,049 to Smitka shows a fastener which is inserted through one sheet of metal in attachment to an edge of another sheet lying perpendicular to the first sheet.
None of these fastening techniques is suitable for use in holding turning vanes in that special fasteners are quite expensive in relation to the cost of the product. Attempts have been made to overcome this by tooling dimples into a rail. In this technique each dimple has a slot through which a sheet metal wall of the turning vane is exposed. The portion of the wall that extends into the dimple is cut in two and bent or crimped in two directions to hold the vane against the rail. This method required extensive labor.
The present invention fulfills the need for a rail for holding turning vanes which does not require special fasteners, which can be inexpensively produced, and which requires minimal labor for the attachment of turning vanes.